We have developed a novel technique for probing the surfaces of cultured cells. Transformed cells labeled with fluorescamine exhibit a striking decrease in fluorescence intensity compared to labeled normal cells. The surface alteration responsible for this difference is one of the earliest measurable parameters of transformation and occurs independently of altered growth rate. It is characteristic of all cells we have examined, including cells transformed by RNA viruses, a DNA virus and a carcinogen. Hyaluronidase treatment of transformed cell surfaces modulates the response to fluorescamine labeling. We propose that, during the early stages of transformation, hyaluronic acid and/or associated mucopolysaccharides and glycoproteins form a surface "barrier", which inhibits the reaction of fluorescamine with cells. We will investigate the nature of this barrier, the implications of its selective permeability for cell surface function and its potential role in the altered behavior of transformed cells. Chromatographic and electrophoretic techniques will be used to analyze the surface mucopolysaccharide composition of cells infected with a temperature sensitive transforming virus. Immunofluorescence microscopy will be used to examine the distribution of hyaluronic acid and its association with other surface components. Alterations in type, relative amounts and distribution of mucopolysaccharides, during transformation, will be correlated with known properties of transformed cells, e.g., decreased fluorescamine labeling, increased glucose uptake and loss of adhesion. A functional role for hyaluronic acid in these parameters will be investigated. We also propose to develop an assay to detect carcinogens, based on the differential labeling of cells with fluorescamine. We have shown that flow cytometry can detect less than 1% transformants within a population of cells and in a pilot study, "transformed" cells were detected within 5 days of treatment with carcinogen. This assay has potential application for the early detection of cancer cells.